I feel like I am back in 1994 and people are trying to manipulate search results for the search engines. I personally think a service such is this is downright bad for the industry, and bad for the users. I saw this on the front page of the forums:
Heh, once I got scolded for directing people to a site where they could get apps for free (and/or get paid for them) and now there's several adds rotating through for similar sites...
For what it's worth, recent news makes it seem like these pay per install services are going the way of the buffalo as Apple is (or was as of a couple days ago) rejecting apps/games that offer incentives to download other apps/games. http://toucharcade.com/2011/04/19/apple-throws-down-the-gauntlet/